—What? cried Mr Dedalus. Were we to desert him at the bidding of the English people?
—He was no longer worthy to lead, said Dante. He was a public sinner.
—We are all sinners and black sinners, said Mr Casey coldly.

During the Christmas dinner in Chapter 1, Mr. Dedalus argues with Dante about the Irish Nationalist movement and the role of Charles Parnell. Mr. Dedalus expresses continued support of Parnell despite his scandalous affair with a married woman while Dante, driven by her religious beliefs, emphasizes the need to abandon him. The national tensions that manifest themselves on a microcosmic level at the Christmas dinner reflect the tight hold that politics has on Mr. Dedalus, a dynamic which young Stephen views with suspicion. 

But we were all gentlemen, Stephen—at least I hope we were—and bloody good honest Irishmen too. That’s the kind of fellows I want you to associate with, fellows of the right kidney. I’m talking to you as a friend, Stephen. I don’t believe a son should be afraid of his father.

When Mr. Dedalus takes Stephen to visit Cork in Chapter 2, he becomes particularly sentimental as he shows his son the places in which he spent his own childhood. Stephen is rather unaffected by his father’s overwhelming nostalgia, but Mr. Dedalus uses their trip as an opportunity to explain to his son the type of man he should aspire to be. While Mr. Dedalus may be sincere in his desire to mentor Stephen, the fact that he wants him to follow in his footsteps, a path which led him to his current, struggling state, is deeply ironic.  

A second shrill whistle, prolonged angrily, brought one of the girls to the foot of the staircase.
—Yes, father?
—Is your lazy bitch of a brother gone out yet?
—Yes, father.
—Yes, father.

When Chapter 5 begins, Mr. Dedalus has lost all sense of compassion and becomes yet another burden which Stephen feels he must escape. The fact that Mr. Dedalus does not physically appear in this scene indicates that he no longer plays an active role in the family, forcing his children to act on his behalf instead. This personal downfall represents the consequences of living a life too inextricably linked to a construct like politics as Mr. Dedalus cannot separate his own emotions from the grim prospects of the Home Rule Movement.